Monitored roller bearing

ABSTRACT

The invention relates to a monitored roller bearing device, comprising a non-rotating race ( 10 ), a rotating race ( 12 ), at least one row of rolling elements ( 14 ) arranged between two rolling tracks ( 11, 13 ) on the rotating race ( 12 ) and non-rotating race ( 10 ) and an information detection module, which comprises a non-rotating sensor unit ( 29 ) and a rotating ( 12 ) encoder ( 28 ). Said device comprises a means for fixing the sensor unit ( 29 ) relative to a support ( 3 ), by generating an axial force between a support surface ( 34   b ) on the sensor unit ( 29 ) and a support surface ( 7 ) on the support ( 3 ), whilst permitting an axial displacement of the sensor unit ( 29 ) relative to the support ( 3 ).

The present invention relates to the field of monitored roller bearingsfitted with a module for detecting the parameters of rotation, such asthe angular position, the direction of rotation, the speed, theacceleration.

The invention relates more particularly to a monitored roller bearingcomprising a sensor secured to a non-rotating race and an encodersecured to a rotating race, the angular position of the sensor beingindexed based on a non-rotating element, so that the angular position ofthe encoder relative to the fixed element is known.

Such roller bearings are used for example for the driving of synchronoustype electric motors. The indexation of the sensor is used to ascertainin particular the speed of rotation and the position of the poles of therotor relative to the poles of the stator.

Through EP A1 1 037 051, a monitored roller bearing is known in which anencoder element is secured to a shaft, an encoder unit being secured toa rotating race. The rotating race is mounted in a bore of a fixedportion in order to allow an axial displacement relative to the fixedportion, shims exerting an axial force on the non-rotating race to keepit in position. The sensor unit is fitted onto the outer surface of thenon-rotating race. Pins disposed axially, projecting into orifices madein the fixed portion and into the sensor, angularly secure the sensorand the non-rotating portion, while allowing an indexation of the sensorrelative to the fixed portion.

Nevertheless, such a device, using on the one hand shims to exert anaxial force on the non-rotating race and on the other hand pins toangularly immobilize the sensor relative to the fixed portion is costlyand difficult to assemble.

The invention proposes a monitored roller bearing device comprisingmeans for angularly immobilizing a non-rotating portion of the device ona support while allowing an axial displacement of the device relative tothe support, having a limited number of pieces, and capable of beingobtained at low cost.

A monitored roller bearing device, of the type comprising a non-rotatingrace, a rotating race, at least one row of rolling elements arrangedbetween two rolling tracks of the rotating race and non-rotating race,and an information detection module comprising a non-rotating sensorunit and a rotating encoder. According to one aspect of the invention,the monitored roller bearing device comprises a means for immobilizingangularly the sensor unit relative to a support, by exerting an axialforce between a support surface of the sensor unit and a support surfaceof the support and by permitting an axial displacement of the sensorunit relative to the support.

Thus, the sensor unit remains angularly immobile relative to the supportin a predefined relative angular position. The means for angularlyimmobilizing the sensor unit on the support is axially preloaded betweena support surface of the sensor unit and a support surface of thesupport to exert an axial force between said support surfaces. Themonitored roller bearing device can be kept in an appropriate angularposition, while allowing an axial displacement within a certain limit ofthe sensor unit relative to the support.

Advantageously, the angular immobilization means also consists of anangular means of indexation of the sensor unit relative to the support.When the sensor unit is installed, the angular indexation of theposition of the sensor unit relative to the support can be used toascertain accurately the angular position of the sensor unit relative tothe support, which will not change thanks to the angular immobilizationmeans.

In one embodiment, the angular immobilization means comprises at leastone axially elastic lug, comprising a first end pressing axially on thesupport surface of the sensor unit, and a second end opposite the firstend and pressing axially on a support surface of the support. Theelastic deformation of the lug, allowing the axial displacement of thesensor unit relative to the support, is accompanied by the generation ofan axial force between the support surface of the sensor unit and thesupport surface of the support.

Advantageously, the angular immobilization means interacts with at leastone groove made on a support surface. In preference a groove is radial.

In one embodiment, the groove is made on the support surface of thesensor unit.

In one embodiment, the groove is made on the support surface of thesupport.

Advantageously, a lug comprises at least one end projecting into agroove made on a support surface. The lug projecting into a groove madeon a support surface allows a link in rotation.

Advantageously, a groove has an open profile, comprising a radial bottomsurface and inclined flange surfaces. Thus, the lug interacts with theinclined flange surfaces of the groove such that the lug projecting intothe radial groove is inserted into the groove until it is insimultaneous contact with the two inclined flange surfaces of thegroove, such that there is no angular clearance between the sensor unitand the elastic lug.

Advantageously, the lug is pressing on inclined flange surfaces of thegroove.

Advantageously, the angular immobilization means comprises a pluralityof axially elastic lugs. The lugs are independent or interlinked. Theuse of a plurality of lugs enable to distribute and balance the forceexerted on a support surface. Depending on the number of lugs, theirprofile and the elasticity of the material used, a greater or lesserforce will be created between the support surfaces as a function of therelative axial displacement of the support surfaces. The linking of thelugs allows the lugs to interact in order to angularly immobilize thesensor unit relative to the support.

In one embodiment, the lugs originate from a ring secured to thesupport. The ring may be in direct contact on one support surface,distributing an axial force over the whole support surface. The use of aring also makes it possible to obtain lugs in a single assembly in orderto facilitate their installation which is done in a single operation forall the lugs.

In another embodiment, the lugs originate from a ring secured to thesensor unit. Preferably, the ends of the lugs furthest from the ring arefree.

The monitored roller bearing device is suitable for use in an electricmotor comprising a stator, a rotor, and a first roller bearing device.

The present invention and its advantages will be better understood onstudying the detailed description of the embodiments taken asnonlimiting examples and illustrated by the appended drawings in which:

FIG. 1 is a view in axial section of a monitored roller bearing device;

FIG. 2 is a partial view in section along II-II in FIG. 1;

FIG. 3 is a view in perspective of the monitored roller bearing devicein FIG. 1; and

FIG. 4 is a view in axial section of a second embodiment of themonitored roller bearing device.

In FIGS. 1 and 3, the monitored roller bearing, referenced 1 in itsentirety, is mounted on an end 2 of a non-rotating shaft 3. Said shaft 3comprises a cylindrical axial portion 4 of external diameter greaterthan the external diameter of the end 2 of the shaft 3. A cylindricalbearing surface 5 is formed between the end of the axial portion 4 andthe end 2 of the shaft 3, and has an external diameter smaller than theexternal diameter of the axial portion 4 while being greater than theexternal diameter of the end 2. A radial support surface 7 extendsbetween the cylindrical bearing surface 5 and the outer surface 6 of theaxial portion 4. A radial surface 8 extends between the cylindricalouter surface 9 of the end 2 of the shaft 3 and the cylindrical bearingsurface 5. The cylindrical bearing surface 5 is threaded on its outersurface.

The roller bearing 1 comprises an inner race 10 provided on its outersurface with a rolling track 11, an outer race 12 provided on its innersurface with a rolling track 13, a row of rolling elements 14, hereballs, arranged between the rolling tracks 11 and 13 of the inner race10 and the outer race 12, and kept circumferentially spaced by a cage15. The outer race 12 comprises on its inner surface two annular grooves16, 17 adjacent to the axial ends opposite the outer race 12. The innerrace 10 is mounted on the outer surface 9 of the end 2 of the shaft 3,with a tight-sliding fit. The roller bearing 1 could comprise aplurality of rows of rolling elements, for example 2. Furthermore,different rolling elements, such as rollers or needles can be used.

A sealing element 18 fixed into the annular groove 17 of the outer race12 axially on the side of the outer race 12 opposite the axial portion 4of the shaft 3, comes into friction contact with the outer surface ofthe inner race 10. The sealing element 18 seals the inner space of thebearing 1, lying radially between inner race 10 and the outer race 12,against the ingress of foreign bodies, or against leaks of lubricant,such as the grease placed in the bearing 1.

A rotating element 19 comprises an axial portion 20 having a bore 20 ainto which the outer race 12 of the bearing 1 is fitted. An annular wall21 extends radially inward from the end of the axial portion 20 of therotating element 19, axially from the side opposite the sealing element18. The outer race 12 of the bearing 1 comprises a front face cominginto axial contact with the annular wall 21 of the rotating element 19.The annular wall 21 of the rotating element 19 has an inner diametergreater than the diameter of the bore of the outer race 2.

A radial side 22 extends radially outward from the end of the axialportion 20 opposite the annular wall 21. The radial side 22 is providedwith drill holes 23 circumferentially spaced and intended to be used forthe attachment of the rotating element 19 onto a unit rotating relativeto the shaft 3, a wheel for example. The rotating element 19 comprisesan annular shoulder 24 extending axially from the zone of least diameterof the radial wall 23, and whose bore 24 a extends the bore 20 a of theaxial wall 20. An annular groove 25 of rectangular profile is partiallyformed in the bore 24 a while protruding axially onto the bore 20 a. Aretention unit 26, of the circlip type, lodged in the groove 25, buttsaxially against a front face of the outer race 12 opposite the face ofthe outer race 12 butting axially against the annular wall 21 of therotating element 19. The annular wall 21 and the retention unit 26axially retain the outer race 12 of the bearing 1 in the bore 20 a ofthe rotating element 19. The outer race 12 is force fitted into the bore20 a of the rotating element 19, the outer race 12 being secured inrotation to the rotating element 19.

A detection module referenced 27 in its entirety comprises an encoderring 28 and a sensor unit 29. The encoder ring 28 comprises an annularportion 30 situated radially in part between the inner race 10 and theouter race 12 projecting axially from the inner space of the bearing 1.The annular portion 30 comprises an inner cylindrical bearing surface31, axially from the side of its end adjacent to the rotating elements14. The annular portion 30 is fitted onto the inner surface of the outerring 12.

The annular portion 30 comprises an annular shoulder 32 projectingradially outward, close to the axial end of the annular portion 30 ofthe side of the rotating elements 14. The annular shoulder 32 projectsradially into the annular groove 16 of the outer race 12, to secure theencoder 28 angularly and axially onto the outer race 12. On the sideopposite its end adjacent to the rotating elements 14, the annularportion 30 extends axially beyond the annular wall 21 of the rotatingelement 19. An active part of the encoder is situated on a portion 33 ofthe outer surface 30 a of the annular portion 30 adjacent to the axialend of the annular portion 30 opposite the annular shoulder 32.

The sensor unit 29 comprises an annular ring 34 disposed axially on thesame side of the bearing 1 as the encoder 28. The annular ring 34 isprovided with a bore 34 a of diameter greater than the outer surface 9of the end 2 of the shaft 3, with a radial support surface 34 b orientedtoward the axial portion 4 of the shaft 3, and with a radial surface 34c axially opposite the radial support surface 34 b. The radial surface34 c comes axially close to the annular wall 21 of the rotating element19 forming a narrow radial passage with the annular wall 21.

An axial shoulder 35 projects axially from the zone of smallest diameterof the radial surface 34 c of the annular ring 34, on the side of thebearing 1. The axial shoulder 35 comprises an end radial surface 35 acoming into axial contact with a front wall of the inner race 10. Anannular ridge 36 extends axially from the zone of greater diameter ofthe axial shoulder 35 and fits onto the outer surface of the inner race10.

The annular ring 34 comprises on the radial surface 34 c an annulargroove 37 of rectangular section, radially adjacent to the axialshoulder 35. The annular portion 30 of the encoder 28 projects axiallyinto the angular groove 37.

The annular ring 34 comprises a detection unit 38 lightly touching theflange surface 37 a of greater diameter of the annular groove 37,radially facing the active portion of the encoder 28 situated on theouter surface of the annular portion 30 of the encoder 28. If the activeportion is a succession of reflective and nonreflective portions, thedetection module 38 is of the optical type. If the active portion is amultipole magnetic ring, the detection module 38 is of themagnetism-sensitive type, for example a Hall effect cell. Other types ofencoders and sensors may be envisaged.

The sealing of the air gap of the detection unit 27, situated radiallybetween the outer surface 30 a of the annular portion 30 of the encoder28 and the detection unit 38, is provided on the one hand by the narrowpassage formed between the radial surface 34 c of the annular ring 34and the annular wall 21 of the rotating element 19, and on the otherhand by the other narrow passage formed radially between the shoulder 35and the annular portion 30 of the encoder 28. Specifically, the ingressof foreign bodies into the air gap of the detection unit 27 coulddisrupt the measurements made by said detection unit 27.

A connection portion 39 projects radially from the annular ring 34. Awire 40 projecting radially toward the outside of the connection portion39 is connected to the detection unit 38 in a manner not shown.

The radial support surface 34 b of the annular ring 34 comprises fiveradial grooves 41, 42, 43, 44, 45, circumferentially regularly spaced.As can be seen in FIG. 2, the radial groove 41, having an open profilesection, comprises a radial bottom surface 46 and inclined flangesurfaces 47, 48. As can be seen in FIG. 3, the groove 41 extendsradially to the outer surface of the annular ring 34. The grooves 42,43, 44, 45 are similar to the groove 41.

An angular immobilization means 49 comprises a ring 50 centered on thebearing surface 5 of the shaft 3 pressing axially on the radial supportsurface 7 of the shaft 3. The immobilization means 49 comprises fivelugs 51, 52, 53, 54, 55 originating from the ring 50.

The lug 51 comprises a first end 51 a connected at the periphery of thering 50, a portion 51 b extending obliquely, radially outward, towardthe radial support surface 34 b of the annular ring 34, and a secondfree radial end 51 c, opposite the first end 51 a, and projecting intothe radial groove 41 of the radial support surface 34 b of the annularring 34.

The free end 51 c of the lug 51 projecting into the radial groove 41 hasinclined surfaces forming a trapezoidal section to interact with theinclined flange surfaces 47, 48 of the radial groove 41. The other lugs52, 53, 54, 55 are similar to the lug 51.

A nut 56 is screwed onto the thread of the bearing surface 5 of theshaft 3, and axially and angularly immobilizes the ring 5 on the radialsurface 7 of the shaft 3. The lugs 51, 52, 53, 54, 55 are then securedin rotation to the non-rotating shaft 3 serving as a support.

Any appropriate means may be envisaged for angularly indexing theangular immobilization means 49 relative to the non-rotating shaft 3before the nut 56 is tightened.

The lugs 51, 52, 53, 54, 55 projecting into the radial groovesrespectively 41, 42, 43, 44, 45, immobilize the rotation of the annularring 34 of the sensor unit 29, relative to the ring 50, and therefore tothe non-rotating shaft 3. The sensor unit 29 is angularly immobilerelative to the shaft 3.

Since the radial grooves 41, 42, 43, 44, 45 have inclined flangesurfaces forming an open trapezoidal profile, the free ends of the lugs51, 52, 53, 54, 55, having a matching shape, project into the grooves41, 42, 43, 44, 45 until each one presses simultaneously on the twoinclined flange surfaces of each radial groove 41, 42, 43, 44, 45. Thissimultaneous contact is used to ensure that there is no angularclearance radially between the sensor unit 29 and the lugs 51, 52, 53,54, 55 as could be the case if the grooves and the lugs had arectangular section. Inclined flange surfaces, like the flange surfaces47, 48, are used to take up the angular clearances. The angular positionof the sensor unit relative to the lugs 51, 52, 53, 54, 55 is thereforeprecise. Naturally, other sections of the grooves and of the lugs aresuitable for producing the same effect of removing the angularclearance.

The slenderness of the lugs 51, 52, 53, 54, 55, the great length of theoblique portions and the elasticity of the material allow the lugs 51,52, 53, 54, 55 to deform axially in such a way as to allow a relativeaxial displacement of the sensor unit 29 relative to the end 2 of theshaft 3, the axial contact between the free ends of the lugs 51, 52, 53,54, 55 and the grooves 41, 42, 43, 44, 45 being constantly maintainedduring the permitted relative axial displacement of the sensor unit 29relative to the shaft 3.

When they deform, the lugs 51, 52, 53, 54, 55 exert by elasticity anaxial force on the radial support surface 34 b of the sensor unit, thering 50 exerting an opposite axial force on the radial support surface 7of the shaft 3. An axial displacement of the sensor unit 29 toward thering 50 causes an increase in the axial force exerted by the lugs 51,52, 53, 54, 55. An axial displacement of the sensor unit 29 on the sideopposite to the ring 50 causes a diminution of the axial force exertedby the lugs 51, 52, 53, 54, 55.

The sensor unit 29 having a shoulder 35 provided with a radial surface35 aresting axially on a frontal surface of the inner race 10 transmitsthe axial forces exerted by the lugs 51, 52, 53, 54, 55 on the radialsupport surface 34 b to the inner race 10.

The diameter of the bore 34 a of the annular ring 34 being greater thanthe diameter of the outer surface 9 of the end 2, the sensor unit 29 canmove freely axially relative to the end 2 of the shaft 3. The sensorunit 29, whose annular ridge 36 is fitted onto the outer surface of theinner race 10, is secured to the inner race 10. The inner race 10 beingmounted with a tight-sliding fit on the outer surface 9 of the end 2 ofthe shaft 3, the race 10 can have an axial movement relative to the end2 of the shaft 3.

Preferably, the lugs 51, 52, 53, 54, 55 are adapted so that, when themechanical assembly is in a normal idle position, the lugs 51, 52, 53,54, 55 exert an axial force on the radial support surface 34 b. Thus,the axial force transmitted by the sensor unit 29 on the inner race 10is used to exert a preload force on the bearing 1 disposed in a normalposition of use. In addition, the lugs 51, 52, 53, 54, 55 can bedimensioned in such a way that, irrespective of the axial position ofthe roller bearing 1 on the end 2 of the shaft 3 when the roller bearingdevice is being used, the lugs 51, 52, 53, 54, 55 exert an axial forceon the radial support surface 34 b. This ensures that the lugs 51, 52,53, 54, 55 will always be in contact with the radial support surface 34b and that the bearing 1 will always be subject, during its use, to apreload force.

During operation of the monitored roller bearing device, if an axialforce applied to the bearing 1 or to the shaft 3 tends to displace thebearing 1 axially relative to the shaft 3, the lugs 51, 52, 53, 54, 55allowing a slight axial displacement by deforming, said lugs 51, 52, 53,54, 55 remaining in contact with the radial surface 34 b of the sensorunit 29 and thus ensuring maintenance of the angular link and of theangular indexation between the sensor unit 29 and the non-rotating shaft3.

The length of the radial grooves 41, 42, 43, 44, 45 is suitable forallowing the deformation of the lugs 51, 52, 53, 54, 55. Specifically,when the sensor unit 29 comes close to the axial portion 4 of the shaft3, the lugs 51, 52, 53, 54, 55 tend to deform by opening radiallyoutward. The free ends of the lugs 51, 52, 53, 54, 55 pressing into thegrooves 41, 42, 43, 44, 45 then slide radially outward in the grooves41, 42, 43, 44, 45. Since the grooves 41, 42, 43, 44, 45 extend to theouter surface of the annular ring 34, the sliding of the lugs 51, 52,53, 54, 55 is not hampered. When the sensor unit 29 tends to move awayfrom the axial portion 4 of the shaft 3, the radial grooves 41, 42, 43,44, 45 must extend radially inward in order to allow the sliding of thelugs 51, 52, 53, 54, 55 which return to a position of lesserdeformation.

Since the lugs 51, 52, 53, 54, 55 project into the radial grooves 41,42, 43, 44, 45 and angularly secure the sensor unit 29 and the shaft 3serving as a support, the sensor unit 29 is oriented angularly relativeto the fixing lugs 51, 52, 53, 54, 55. Preferably, the ring 50 of theimmobilization means 49 may itself comprise a means of indexation of thering 50 on the shaft 3, such as a tab projecting into an axial groovemade on the bearing surface 5 of the shaft 3. Thus, the angular positionof the ring relative to the shaft 3 is precisely defined, such that theangular position of the sensor unit 29 and therefore of the detectionmodule 38 relative to the shaft 3 is also precisely known.

The ring 50 could be secured to the shaft 3 by a means other than thenut 56. For example, since the immobilization means 49 is suitable to bepreloaded, the ring 50 permanently sustains a force which moves it closeto the radial surface 7. Bonding could suffice to attach the ring 50. Itcould also be secured by a ratchet mechanism, an annular groove adjacentto the radial surface 7 being formed on the outer surface of thecylindrical bearing surface 5, a lug originating from the ring 5extending obliquely on the side opposite the radial surface 7, radiallyinward, and having an end in friction contact with a flange surface or abottom surface of the annular groove to angularly secure the ring 50 andthe shaft 3. The elastic deformation of the lug allows the ring to beinserted, until the lug is released in the annular groove and preventsan inverse axial movement of the ring 50.

It is possible to envisage that the lugs 51, 52, 53, 54, 55 becircumferentially irregularly spaced, in order to easily determine theappropriate and unique angular position of the sensor unit 29 relativeto the shaft 3. It is also possible to envisage other means, such asfoolproof devices or marks, to allow an angular orientation of thesensor unit when the roller bearing device is assembled.

Since the angular immobilization means 49 is used to immobilize andindex the sensor unit 29 angularly relative to the shaft 3, anaccidental rotation of the inner race 10 relative to the sensor unit 29will not cause an angular movement of the sensor unit 29 relative to theshaft 3, thus not disrupting the position measurements made by thedetection module 27.

Radial grooves 41, 42, 43, 44, 45 have been provided. Non-radial groovesand corresponding lugs 51, 52, 53, 54, 55 could of course be providedwithout departing from the scope of the invention.

In FIG. 4, the references of similar elements have been reused. Theangular immobilization means 49 comprises a ring 61 of large diameterdisposed in an annular recess 62 made on the radial surface 34 b of thesensor unit 29, said ring 61 being attached to the sensor unit by meansof screws symbolized by dot-and-dash lines in FIG. 4 for better clarityof the drawing. Five lugs, of which only the lugs 63 and 64 are visiblein the figure, originate from the ring 61. Since the lugs are identical,only lug 63 is described in detail.

The lug 63 comprises a first end 63 a connected to a zone of lesserdiameter of the ring 61, a portion 63 b extending obliquely, radiallyinward, toward the radial surface 7 of the shaft 3. The lug 63 comprisesa second free radial end 63 c, opposite the first end 63 a, projectinginto a radial groove 65 made on the radial surface 7 of the shaft 3.Each lug of the angular immobilization means 49 is associated with aradial groove made in the radial surface 7. The operation of the secondembodiment of the roller bearing device is similar to the mode ofoperation of the first embodiment. The dimensions of the radial groove65 are adapted so as not to hamper the deformation of the lug 63 byallowing the second end 63 c of the lug 63 to slide radially in thegroove 65.

A description has been given of the embodiments in which the lugs havetwo ends: one free end projecting into a groove made in a supportsurface and one end embedded in a ring attached on an opposite supportsurface. In another embodiment, the lugs are not connected by a ring.Each lug is independent and has one free end projecting into a groovemade in a support surface and one end attached to an opposite supportsurface. The end attached to a support surface may also project into agroove made on said support surface. The attached end may be the end incontact with the support surface of the support, or the end in contactwith the support surface of the sensor unit.

Again provision can be made for the two ends of a lug to be attached tothe corresponding support surfaces, one end or both ends projecting intoa groove, or no groove being provided. Again provision can be made forthe two ends of a lug to be embedded in a ring attached to thecorresponding support surface.

The angular immobilization means has been described as comprisingseveral lugs. Naturally, an angular immobilization means comprising asingle lug could be suitable.

The monitored roller bearing device, according to the invention, is usedto angularly immobilize the sensor unit relative to a support, whiletransmitting an axial force between a radial surface of the support anda radial surface of the sensor unit. It is also possible to obtain amonitored roller bearing allowing an axial displacement of the monitoredroller bearing relative to the support. It is also possible, with thesame device, to obtain an angular indexation of the sensor unit relativeto the support. The monitored roller bearing device thus obtained,having a limited number of pieces, has a low cost of production and canbe assembled in a limited number of operations.

1. An instrumented rolling bearing device, of the type comprising anon-rotating race, a rotating race, at least one row of rolling elementsarranged between two raceways of the rotating race and non-rotatingrace, an information detection module comprising a non-rotating sensorunit and a rotating encoder, and a means for immobilizing angularly thesensor unit relative to a support, by permitting an axial displacementof the sensor unit relative to the support, and wherein, the angularimmobilization means exerts an axial preloading force between a supportsurface of the sensor unit and a support surface of the support.
 2. Thedevice as claimed in claim 1, wherein the angular immobilization meansalso constitutes a means of angular indexation of the sensor unitrelative to the support.
 3. The device as claimed in claim 1, whereinthe angular immobilization means comprises at least one axially elasticlug comprising a first end pressing axially on the support surface ofthe sensor unit, and a second end opposite the first end and bearingaxially on a support surface of the support.
 4. The device as claimed inclaim 1, wherein the angular immobilization means interacts with atleast one groove made in a support surface.
 6. The device as claimed inclaim 4, wherein the groove is made on the support surface of the sensorunit.
 7. The device as claimed in claim 4, wherein the groove is made onthe support surface of the support.
 8. The device as claimed in claim 4,wherein a lug comprises at least end projecting into a slot made on asupport surface.
 9. The device as claimed in claim 4, wherein a groovepossesses an open profile, comprising a radial web surface and inclinedflange surfaces.
 10. The device as claimed in, claim 8, wherein a lug ispressing on the inclined flange surfaces of a groove.
 11. The device asclaimed in claim 1, wherein the annular immobilization means comprises aplurality of axially elastic lugs.
 12. The device as claimed in claim11, wherein the lugs originate from a ring secured to the support. 13.The device as claimed in claim 11, wherein the lugs originate from aring secured to the sensor unit.
 14. An electric motor comprising astator, a rotor, a first rolling bearing device and a second rollingbearing device as claimed in claim 1.